I have recently come across the book Modern Methods in the Calculus of Variations: $L^p$ Spaces by Irene Fonseca and Giovanni Leoni. From section "About this book",
This is the first of two books on methods and techniques in the calculus of variations. Contemporary arguments are used throughout the text to streamline and present in a unified way classical results, and to provide novel contributions at the forefront of the theory.
This book addresses fundamental questions related to lower semicontinuity and relaxation of functionals within the unconstrained setting, mainly in $L^p$ spaces. It prepares the ground for the second volume where the variational treatment of functionals involving fields and their derivatives will be undertaken within the framework of Sobolev spaces.
From section "Review",
"This book is the first of two volumes in the calculus of variations and measure theory. The main objective of this book is to introduce necessary and sufficient conditions for sequential lower semicontinuity of functionals on Lp-spaces. … This book is very nicely written, self-contained and it is an excellent and modern introduction to the calculus of variations." (Jean-Pierre Raymond, Zentrablatt MATH, Vol. 1153, 2009)
“This is the first of a two-volume introduction into direct methods in the calculus of variations. Its main topic is the analysis of necessary and sufficient conditions for lower semicontinuity on Lp-spaces, as well as of relaxation techniques. … The book provides a well-written and self-contained introduction to an active area of research and will be valuable both to graduate students as an introduction and to researchers in the field as a reference work.” (M. Kunzinger, Monatshefte für Mathematik, Vol. 156 (4), April, 2009)
Could you elaborate on which is the second volume?
It is mentioned at the personal website of the second author that